We don't have evidence that any animal other than ourselves "wants" to do anything, yet we attribute that to other human beings and some animals regardless. Assuming you don't adhere to solipsism, your line of reasoning doesn't make any sense.
That's simply incorrect. Animals are capable of responding to sensory inputs with a clear preference for one alternative over another. For example, a cat will run away from a dog, which is evidence that it does not want to get bitten.
Individual cells have no such autonomy.
Tom did not base his claim on the idea of there being a hypothetical being in the future. Do not put words in his mouth just to form your own baseless arguments.
Actually, he did:
How many foster children can you find who would say "I would rather have been an abortion!" Kids find a way to enjoy life, even if they are a foster child. Even if they happened to be one of those unfortunate kids who were abused, they would likely get past that at some point and enjoy life. Is some hypothetical physical or sexual abuse really worth a death sentence?
It is not certain that an embryo will develop into a foster child, just as it is not certain that a sperm will fertilise an ovum to develop an embryo. Tom's argument is based on hypothetical future outcomes.
As to the moment life begins, I believe it's always there.
There is no "moment life begins"; life is continuous from parent to child. A sperm is just as alive as a newborn baby, which is just as alive as an apple tree. If you have ever picked an apple, you have destroyed life in precisely the same way as an abortion practitioner.
This is a common line of reasoning among anti-abortionists, who try to boil down the issue to being about the preservation of life. It is not about life unless you are also campaigning against the harvesting of crops. It is about a sapient human being, and the question you should ask is at what point sapience begins, not what point life begins.
Don't get me wrong, I'm not attacking pro-lifers here exclusively. Pro-choicers also like to try to make the issue more black and white than it appears, by boiling the subject down to women's rights and simply ignoring the pro-life argument.
Both sides need to realise that it is not a black and white issue, but a matter of degrees, for which one extreme would ban birth control and the other would legalise killing babies. Most people fall somewhere in the middle.